The present invention relates generally to reclosable flexible plastic containers and in particular to reclosable flexible containers having fastener profiles affixed to the exterior of the container.
In the manufacture of reclosable plastic bags, the bags are usually formed with a folded bottom edge and with side edges sealed to each other. Flexible reclosable plastic fastener strips are usually sealed inside the top edges of the bag. Alternatively, fastener profiles may be integrally formed in the plastic film, as seen in U.S. Reissue Pat. No. 28,959; Naito. The fastener strips may take forms such as shown in U.S. Pat. No. 2,780,261, Svec et al and U.S. Pat. No. 4,430,070; Ausnit, as well as various other configurations.
In the manufacture of bags such as illustrated in Svec et al., the bag bodies are formed of a thin lightweight plastic film which is extruded separately from the fastener. The fastener strips are extruded with a process that provides interlocking rib and groove elements carefully shaped and sized so that they will interlock when pressed together and will separate when pulled apart by opening flanges. These strips have webbed portions which are sealed to the film of the bag. The bags in question can be manufactured in a multiple operation so that two bag bodies, in one embodiment, project from the center of a single web of plastic material. By cross-cutting and slitting along the length of the material, two bags are formed simultaneously. Since the overall cost of completed bags are a function of the speed at which they can be manufactured, this method reduces costs. However, problems have appeared in the past in the sealing of the fastener strips to the film. The amount of heat used in joining the fasteners to the bag wall has an effect on the seal. If insufficient heat is applied, the seal will be inadequately formed so that the bag will leak, or the fastener web will peel away from the film to which it is attached. If too much heat is applied, the plastic will melt away so that there may be holes in the wall of the bag. It is also important for the fastener strips and the bag film to be accurately orientated with respect to each other. These requirements have resulted in reducing the speed of manufacture and increasing the cost.
Accordingly, it is the object of the present invention to provide a method of manufacturing reclosable plastic containers without the need for a continuous accurate seal of the fastener profiles to the inner surface of the containers.
It is an additional object of the invention to provide a reclosable plastic container which facilitates the precise orientation of the fastener profiles during manufacture.
It is an additional object of the present invention to provide a method of manufacturing reclosable plastic containers which is low in cost, high speed, and which reduces the quantity of containers rejected.
Others objects, advantages and features and equivalent structures within the scope of the invention will become apparent to those skilled in the art in connection with the teachings of the principles thereof in the specification, claims and drawings.